<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div id="app">
  <h1>{{info}}</h1>
</div>

<script src="vue.js"></script>
<script>
  let v = new Vue({
    el:"#app",
    data:{
      info:"Hello Vue！"
    }
  })

  setTimeout(function () {
      v.info = "值改变了";
  },3000)
</script>
</body>
</html>